My brother-in-law purchased a magnetic bracelet and swears that it works in making him more 'balanced' and 'stronger'. To prove it's effects he made me stand with my feet about a foot apart and pulled my right arm down and away from me. This caused me to lean over and take a step. Then he put the magnet on my wrist and repeated the experiment. Of course, this time it was much harder for him to pull me over (because I knew what was coming).

Obviously I could have him repeat the experiment in the reverse order on a new person to prove that this 'test' is worthless, but I doubt he will be convinced. Part of the problem is that he'll argue that it works 'for him' and may not work for other people. He also may have a small aversion to me presenting the argument, since agreeing with me would then mean he'd have to admit he was duped.

Putting aside the question of whether I really want to get into this argument with my brother-in-law, is there a simple way to prove to him that the magnet is not making him stronger?

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@Fabian I think this question is a good example of why such questions should be on-topic.
– Konrad RudolphMar 7 '11 at 20:31

2

@Konrad On reconsidering this specific question, I think it is different because one can also ask it as "Which simple experiment can I perform to show that magnets don't make you stronger", which I would consider on-topic. The question "How can I convince my brother-in-law" is off-topic in my opinion.
– Mad Scientist♦Mar 7 '11 at 20:36

It's going to be very hard to prove to any single individual that something like that doesn't work -- due to the Placebo effect. He may very well be experiencing a benefit from the magnets. He'd also be quite right to say they work for him and not others, since the effect is entirely in his own psychology.

If he won't respond to evidence (research studies, etc.) then there is little you can do to convince him, but I'll look for some papers on it for you.

First, put the magnetic band in a bag, and put it close to your brother-in-law's body. Re-run the tests he did, to establish that the magnetic band still works in a bag, when your brother-in-law knows it is in there. Do this first, so there can be no complaints later that the bag interfered.

Then, repeat the following experiment several times:

In another room, have one person put the magnetic band in one bag, and something about the same size and weight in another identical bag. That person should stay out of the room.

Have another person, who doesn't know which is which, put each bag in turn close to his body, and do the tests, and record which bag succeeds better.

Then, and only then, look in the bags to see which one is which.

If your brother-in-law is right, he should be able to tell which one is which much more often than he gets it wrong. If he is wrong, it should be approximately 50-50.

It's important that the allocation to the bags is unpredictable (random). It is important that neither your brother-in-law nor the person in the room doing the test know which bag contains the real magnetic band (double-blind). And it is important to compare both with and without the band - which you were already doing (controlled). It is also important that the person in the room have no idea what the test is, or what the bands are (to complete the double blind).

Well, a mean way would be to demagnetize his bracelets without telling him.

If he still feels more "balanced" and "stronger" it would indicate that magnetism didn't have anything to do with it. (Of course he could argue that wearing the bracelets for so long has changed something in his body permanently by now, thus making a continuous stimulation through a magnetic field obsolete.)